Intestinal absorbability of wheat allergens, subunits of a wheat alpha-amylase inhibitor, expressed by bacteria

Wheat CM2, CM3 and CM16 proteins are known as subunits of the tetrameric alpha-amylase inhibitor as well as major allergens to baker's asthma. The purpose of this study is to produce these CM proteins by bacteria in a quantity adequate for studying the penetration characteristics of the CM proteins through intestinal mucosa in rats and Caco-2 cells. cDNAs encoding the mature proteins were expressed in Escherichia coli and purified by an Ni2+-chelating column. The recombinant proteins were radioiodinated and admministered orally to rats or applied to the apical site of the Caco-2 cell monolayer. The radioactivity in the trichloroacetic acid-insoluble fraction, which was mainly composed of peptides with molecular mass less than that of the intact CM proteins, in the serum and the basolateral medium was highest in recombinant CM3. Accordingly, the intestinal absorption of these three proteins in the form present in wheat should be evaluated.